Biology · Edexcel Paper 2
Homeostasis
How the body keeps its internal conditions steady by negative feedback, why enzymes and animal cells need constant temperature and water content, how the skin and the hypothalamus control body temperature, how insulin and glucagon control the level of glucose in the blood, what causes type 1 and type 2 diabetes, and how BMI and the waist to hip ratio link to type 2 diabetes. Matches Edexcel 7.9 to 7.17. Homeostasis (7.9), insulin (7.13), diabetes (7.15, 7.16) and BMI (7.17) are for both Combined Science and separate Biology. The importance of homeostasis (7.10B) and the skin (7.11B, 7.12B) are marked B, so they are for separate Biology only. Glucagon (7.14), and vasoconstriction and vasodilation (7.12B parts b and c) are for the Higher tier only.
Lessons
Ticks are remembered on this device only.
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1
Maintaining a Constant Internal Environment
Whatever the weather, and whether you are asleep or sprinting, your body temperature stays close to 37 °C. This lesson explains homeostasis, the control of the…
9 terms -
2
Why Homeostasis Matters: Enzymes and Osmosis
Two things go wrong very quickly if the internal environment is not controlled: the enzymes stop working, and the cells gain or lose water. This lesson is for…
9 terms -
3
Thermoregulation and the Skin
When you are hot your skin sweats, and when you are cold you shiver. This lesson is for separate Biology only: Combined Science students do not need it. It…
9 terms -
4
Vasoconstriction and Vasodilation (Higher tier)
The skin of a hot, tired runner is red and flushed, while the fingers of a person in the snow turn white. This lesson is for separate Biology only, and for the…
9 terms -
5
Insulin and Blood Glucose
After a meal, a lot of glucose enters the blood, but the level soon returns to normal. This lesson explains how the hormone insulin controls the concentration…
9 terms -
6
Glucagon and Blood Glucose (Higher tier)
Between meals, and during exercise, the blood glucose concentration can fall, and then a second hormone comes into play. This lesson is for the Higher tier…
9 terms -
7
Type 1 and Type 2 Diabetes
Diabetes is one of the most common long-term diseases in the world, and its two main forms have different causes and different treatments. This lesson explains…
9 terms -
8
Body Mass, BMI and Type 2 Diabetes
People who are very overweight are much more likely to develop type 2 diabetes. This lesson explains how to calculate the body mass index (BMI) and the waist…
9 terms -
Knowledge organiser
The whole chapter on a page or two of A4 — to revise from on screen or print.
Key terms in this chapter
All 72, gathered from every lesson.
- Homeostasis
- The regulation of the conditions inside the body, so that they stay constant.
- Internal environment
- The conditions inside the body, such as temperature and blood glucose.
- Stimulus
- A change that is detected by a receptor.
- Receptor
- A cell that detects a stimulus.
- Coordination centre
- The part of a control system that receives information and decides on the response.
- Effector
- A muscle or gland that carries out a response.
- Negative feedback
- A response that reverses a change, and returns a condition to its normal level.
- Hormone
- A chemical messenger that is made in a gland and carried in the blood.
- Enzyme
- A biological catalyst that speeds up a reaction in cells.
- Thermoregulation
- The control of body temperature.
- Osmoregulation
- The control of the water content of the body.
- Optimum temperature
- The temperature at which an enzyme works fastest.
- Denatured
- Changed in shape, so that an enzyme can no longer work.
- Active site
- The part of an enzyme where the substrate fits.
- Osmosis
- The net movement of water across a partially permeable membrane from a dilute to a more concentrated solution.
- Dilute
- Containing a lot of water, and a low concentration of solute.
- Concentrated
- Containing less water, and a high concentration of solute.
- Partially permeable
- Letting some substances through, but not others.
- Epidermis
- The thin outer layer of the skin.
- Dermis
- The layer of the skin below the epidermis, which contains sweat glands, blood vessels and receptors.
- Hypothalamus
- The part of the brain that monitors body temperature and coordinates the response.
- Sweat gland
- A gland in the dermis that releases sweat.
- Evaporation
- The change of a liquid into a gas, which takes in heat from the surroundings.
- Shivering
- Rapid, uncontrolled contractions of the muscles, which release heat.
- Hair erector muscle
- A muscle in the dermis that moves a hair.
- Thermoregulation
- The control of body temperature.
- Temperature receptor
- A cell in the skin that detects temperature.
- Vasodilation
- The widening of the blood vessels in the skin, so that more heat is lost.
- Vasoconstriction
- The narrowing of the blood vessels in the skin, so that less heat is lost.
- Radiation
- The transfer of heat from a warm object to its cooler surroundings.
- Dermis
- The layer of the skin that contains the blood vessels and the sweat glands.
- Hypothalamus
- The part of the brain that coordinates the control of body temperature.
- Core temperature
- The temperature of the organs deep inside the body.
- Negative feedback
- A response that reverses a change.
- Effector
- A muscle or a gland that carries out a response.
- Thermoregulation
- The control of body temperature.
- Insulin
- A hormone that is made in the pancreas, which lowers the blood glucose concentration.
- Pancreas
- A gland that makes insulin, glucagon and digestive enzymes.
- Blood glucose concentration
- The amount of glucose in the blood, in mmol per dm³.
- Glycogen
- A storage carbohydrate, which is made from glucose in the liver and muscles.
- Liver
- An organ that stores glycogen, and converts glucose to glycogen.
- Negative feedback
- A response that reverses a change.
- Target cell
- A cell that has receptors for a hormone, and responds to it.
- Digestion
- The breakdown of food into small, soluble molecules.
- Absorption
- The movement of digested food into the blood.
- Glucagon
- A hormone made in the pancreas that raises the blood glucose concentration.
- Glycogen
- A storage carbohydrate, made from glucose, in the liver and muscles.
- Insulin
- A hormone made in the pancreas that lowers the blood glucose concentration.
- Pancreas
- A gland that makes insulin and glucagon.
- Liver
- The organ that stores glycogen, and releases glucose.
- Negative feedback
- A response that reverses a change.
- Antagonistic
- Having opposite effects, as insulin and glucagon do.
- Target organ
- An organ that responds to a hormone.
- Fasting
- Not eating for a period of time.
- Diabetes
- A condition in which the blood glucose concentration is not controlled properly.
- Type 1 diabetes
- Diabetes in which the pancreas does not produce enough insulin.
- Type 2 diabetes
- Diabetes in which the body cells no longer respond to insulin.
- Insulin
- A hormone that lowers the blood glucose concentration.
- Insulin resistance
- A condition in which cells do not respond properly to insulin.
- Obesity
- A condition in which a person has a large amount of excess body fat.
- Insulin pump
- A device that delivers insulin under the skin.
- Immune system
- The body system that defends against pathogens.
- Blood glucose concentration
- The amount of glucose in the blood.
- Body mass index
- A measure of mass for height, calculated as mass in kilograms divided by height in metres squared.
- Waist to hip ratio
- The waist circumference divided by the hip circumference.
- Obesity
- A condition in which a person has a large amount of excess body fat, with a BMI of 30 or more.
- Correlation
- A link between two variables.
- Positive correlation
- A link in which one variable rises as the other rises.
- Insulin resistance
- A condition in which cells do not respond properly to insulin.
- Confounding factor
- A variable, other than the one being studied, that can affect the result.
- Risk factor
- Something that increases the chance of getting a disease.
- Abdomen
- The part of the body between the chest and the hips.